Journal of Nuclear Energy. Part C, Plasma Physics, Accelerators, Thermonuclear Research, 1962
Tetra-t-butyl-s-indacene is a twelve-membered fused-ring compound; the stabilization oftbe compou... more Tetra-t-butyl-s-indacene is a twelve-membered fused-ring compound; the stabilization oftbe compound by bulky r-butyl groups is discussed. The distribution of bonding electron density is depicted in terms of deformation density using the experimental x-x method, a multipole expansion model and a calculation according to the extended Hiicke1molecular orbital method (EHMO). The molecules crystallize according to the space group P2 1 /n with cell parameters a =9.700(3), b =11.746(3), c == 10.858(2)A, f3 = 107.67(2)°, Z = 2 at lOOK. The molecule has a center of inversion(i) and belongs to the symmetry point group Cj• The packing of two unique t-butyl groups in the asymmetric unit appears significantly different However, the map of deformation density in the plane of the ring shows pseudo D 2b symmetry. The accumulation of density at the midpoint of the bonds is observed as expected. The theoretical deformation densities agree with the experimental ones. Analyses of the molecular-orbital wavefunctions provide a good illustration of the aromatic x-electron system. A theoretical study of a series of substituents (-H,-CH J ,-t-butyl) on s-indacene illustrates the stabilization effect ofthe t-butyl group on the 12-n-electron ring system.
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